import java.util.Scanner;
public class Main{
public static void main (String[] args){
	Scanner sc = new Scanner(System.in);
	int n = sc.nextInt();
	int[] a = new int[n];
	for(int i = 0; i < n; i++) {
		a[i] = sc.nextInt();
		}
	int m = sc.nextInt();
	int p = 0;
	boolean f = false;
	for(int i = 0; i < n ; i++) {
		
		if(m == a[i]) {
			p = i + 1;
			f = true;
		}
	}
	if(f == false) {
		System.out.print(-1);	
	}else {
		System.out.print(p);
	}
	
	
	

}
}
/**************************************************************
	Problem: 1815
	User: admin
	Language: Java
	Result: Accepted
	Time:770 ms
	Memory:39628 kb
****************************************************************/